Electronically commutated motors have been used to drive various types of apparatus, such as pumps, by directly or indirectly coupling a shaft extending from the rotor assembly of the motor to the drive shaft of the pump. As the piston or impeller of the pump is in contact with the fluid to be pumped a fluid seal is needed around the pump drive shaft or extension thereof to prevent fluid leakage. Such fluid seals generally require maintenance and wear with use thus increasing the likelihood of fluid leakage.
One of the most widely used types of pump is the automotive "water" (antifreeze/coolant) pump in which a pulley keyed to a shaft carrying the pump impeller is driven by the automobile engine via a belt and pulley coupling. Such pumps require fluid seals around the pump shaft which present a significant maintenance problem. Existing conventional water pumps tend to have the seals and bearings fail long before other engine components. A significant factor in such failures is the side load on bearings and seals from the belt and pulley drive, and this tends to allow pressurized coolant to leak out of the system and cause bearing seizure. Replacement costs in both labor and parts is high.
As such pumps can only operate when the engine is operating, pumping of the fluid through the cooling system ceases when the engine stops resulting in sharply rising engine block temperatures from the heat being built up in the fluid within the block. There is a concommitant and excessive under-hood temperature increase, particularly in transverse mounted engines, front wheel drive automobiles and other engines which have high operating temperatures to reduce hydrocarbon and carbon monoxide emissions. Increased under-hood temperatures significantly reduce the useful life of rubber and plastic parts in the engine compartment.
Additionally, such pumps always operate when the engine is operating thereby requiring thermostatic valves to control fluid flow within the cooling system. Thermostatic valves inhibit fluid flow until the fluid reaches operating temperature so that the engine and fluid surrounding it quickly reach the optimum operating temperature.